Sisters Ju-young and Ju-hee move into a new apartment. Their ordinary lives take a nightmarish turn when Joo-hee mysteriously vanishes from their apartment without a trace. With mounting dread and an ever-present, disturbing noise in the background, Ju-young and Ju-hee`s boyfriend Ki Hoon embark on a harrowing mystery to find Joo-hee and uncover the source of the unsettling sounds. It leads to a dark secret and the revelation of a mysterious entity.